In this application we seek to develop better vectors and reagents that will improve the therapy of pancreatic cancer. Pancreatic cancer is the fifth leading cause of cancer death in the US and accounts for approximately 29,000 deaths per year in the United States and 50,000 deaths per year in Europe (excluding the former USSR). Median survival is six months or less, and only four percent of patients are alive five years after diagnosis. Thus, incidence and death rates are virtually identical. One approach to the treatment of this devastating disease is gene therapy. However, it is widely believed that gene therapy will not succeed until vectors are endowed with the ability to target tumor cells. As will be described in the application, Sindbis viral vectors can systemically target and specifically infect tumor cells in vivo. However, they require further study to enhance these capabilities. To do so we seek to accomplish the following: (Aim 1) To use multiple imaging modalities, including IVlS, MRI, microCT, microSPECT, and microPET to monitor in vivo, in two different mouse models of pancreatic cancer, the extent and specificity of targeting and antitumor efficacy of various Sindbis vectors (generated in Aim 2). (Aim 2) To generate rationally designed Sindbis vectors that can be tested in the two animals models of Aim 1, with the goal of maximizing vector targeting and efficacy. The goal of Aim 2 is to design and develop Sindbis vectors that can induce complete remission in pancreatic cancers and their metastases through a combination of (a) the vector's known apoptosis-inducing potential, (b) the therapeutic payload they encode, and (c) their customizable targeting capabilities. In vivo monitoring of the targeting and efficacy of the new vectors, as discussed in Aim 1, will be critical to achieving this goal. (Aim 3) To examine the effects of the immune system on Sindbis-vector mediated therapy in an immunocompetent mouse model. Such studies will play a role in the design, generation and selection of Sindbis vectors created in Aim 2. (Aim 4) To perform pharmacokinetic studies with the Sindbis vectors to be used for vector-mediated therapy in immunocompetent mice. Such studies will help guide the design, generation and selection of Sindbis vectors created in Aim 2.